Multimode ion mirror prism and energy filtering apparatus and system for time-of-flight mass spectrometry

Abstract

A mass analyzing apparatus and system are disclosed for time-of-flight (“TOF”) mass spectrometry analysis. A representative system includes a first electrostatic mirror prism to reflect a first ion beam and provide an intermediate ion beam having an intermediate TOF focus and having a spatial dispersion of ions proportional to ion kinetic energies; and a second electrostatic mirror prism to reflect the second ion beam and converge the spatial dispersion of ions to provide a third, recombined ion beam having an output TOF focus; and an ion detector arranged at the output TOF focus to receive and detect the ions of the third ion beam. A bandpass filter may be arranged at the intermediate TOF focus to selectively allow propagation of ions of the second ion beam having a selected range of ion kinetic energies. Configurations having additional electrostatic mirror prisms are disclosed, including for tandem MS-MS and selectable time-of-flight.

It is claimed: 
     
       1. A mass analyzing system for time-of-flight (“TOF”) mass spectrometry analysis, the system coupleable to a pulsed ion source providing a first, pulsed ion beam having an input TOF focus, the system comprising:
 an electrostatic mirror prism arrangement comprising:
 a first electrostatic mirror prism having a first plurality of planar electrodes to generate a first retarding electric field to reflect the first ion beam and provide a second, intermediate ion beam having a spatial dispersion of ions proportional to ion kinetic energies, the second ion beam having an intermediate TOF focus; and 
 a second electrostatic mirror prism spaced apart from the first electrostatic mirror prism by a first predetermined distance and further arranged to have a predetermined first angular offset from the first electrostatic mirror prism, the second electrostatic mirror prism having a second plurality of planar electrodes to generate a second retarding electric field to reflect the second ion beam and converge the spatial dispersion of ions to provide a third, recombined ion beam, the third ion beam having an output TOF focus; and 
 
 an ion detector arranged at the output TOF focus to receive the third ion beam, the ion detector adapted to detect a plurality of ions of the third ion beam. 
 
     
     
       2. The system of  claim 1 , wherein the detector is further adapted to detect ion impact position on the detector surface to generate a stigmatic image of a cross-section of the third ion beam. 
     
     
       3. The system of  claim 1 , wherein the predetermined first angular offset is ninety degrees. 
     
     
       4. The system of  claim 1 , wherein the third, recombined ion beam has cancelled the spatial dispersion of ions of the second, intermediate ion beam. 
     
     
       5. The system of  claim 1 , wherein the electrostatic mirror prism arrangement further comprises:
 a bandpass filter having a moveable energy bandpass control slit, the bandpass filter arranged at the intermediate TOF focus to selectively allow propagation of ions of the second ion beam having a selected range of ion kinetic energies. 
 
     
     
       6. The system of  claim 1 , wherein the first plurality of electrodes and the second plurality of electrodes each comprises:
 a first, front electrode having a first, ground electrical potential; 
 a second electrode having a second electrical potential; 
 a third, rear electrode having a third electrical potential; and 
 a plurality of intermediate electrodes, each coupled to one of the second and third electrodes via a resistive voltage divider such that each of the plurality of intermediate electrodes has a respective electrical potential different from the first, second, and third electrical potentials. 
 
     
     
       7. The system of  claim 1 , wherein each electrode of the first plurality of electrodes and the second plurality of electrodes comprise at least one electrode type selected from the group consisting of: a grid electrode, a solid electrode, a solid electrode having a central opening, and combinations thereof. 
     
     
       8. The system of  claim 1 , wherein the electrostatic mirror prism arrangement further comprises:
 a first reflectron arranged spaced apart from the first electrostatic mirror prism in a first direction; and 
 a second reflectron arranged spaced apart from the second electrostatic mirror prism in a second direction opposite the first direction; 
 wherein the first and second reflectrons each have a corresponding central axis, the first and second reflectrons further arranged with each central axis aligned and coextensive with the second ion beam. 
 
     
     
       9. The system of  claim 8 , wherein when the first and second electrostatic mirror prisms are in an off state, the second ion beam is reflected between the first and second reflectrons to provide a selectable number of reflections proportional to a selected time-of-flight. 
     
     
       10. The system of  claim 9 , further comprising:
 a processor coupled to the electrostatic mirror prism arrangement, the processor adapted to control on and off states of the first and second electrostatic mirror prisms to determine the number of reflections between the first and second reflectrons in response to the selected time-of-flight. 
 
     
     
       11. The system of  claim 10 , wherein when the second electrostatic mirror prism is in an on state, the second ion beam is reflected to provide the third ion beam. 
     
     
       12. The system of  claim 1 , wherein the electrostatic mirror prism arrangement further comprises:
 a third electrostatic mirror prism having a third plurality of ion-transparent planar electrodes to generate a third retarding electric field to reflect the first ion beam or a seventh ion beam and provide a fourth ion beam having a spatial dispersion of ions proportional to ion kinetic energies, the fourth ion beam having a fourth TOF focus; 
 a fourth electrostatic mirror prism spaced apart from the third electrostatic mirror prism by a second predetermined distance and further arranged to have a predetermined second angular offset from the third electrostatic mirror prism, the fourth electrostatic mirror prism having a fourth plurality of planar electrodes to generate a fourth retarding electric field to reflect the fourth ion beam and converge the spatial dispersion of ions to provide a fifth, recombined ion beam, the fifth ion beam having a fifth TOF focus; 
 a fifth electrostatic mirror prism having a fifth plurality of electrodes to generate a fifth retarding electric field to reflect the fifth ion beam and provide a sixth ion beam having a spatial dispersion of ions proportional to ion kinetic energies, the sixth ion beam having a sixth TOF focus; and a sixth electrostatic mirror prism spaced apart from the fifth electrostatic mirror prism by a third predetermined distance and further arranged to have a predetermined third angular offset from the fifth electrostatic mirror prism, the sixth electrostatic mirror prism having a sixth plurality of ion-transparent planar electrodes to generate a sixth retarding electric field to reflect the sixth ion beam and converge the spatial dispersion of ions to provide the seventh, recombined beam, the seventh ion beam having a seventh TOF focus collocated with the first TOF focus. 
 
     
     
       13. The system of  claim 12 , wherein when the third electrostatic mirror prism and the sixth electrostatic mirror prism are in an off state, the first ion beam is transmitted to the first electrostatic mirror prism. 
     
     
       14. The system of  claim 12 , wherein when the third electrostatic mirror prism is in an off state, the seventh ion beam is transmitted to the first electrostatic mirror prism. 
     
     
       15. The system of  claim 12 , wherein when the third electrostatic mirror prism, the fourth electrostatic mirror prism, the fifth electrostatic mirror prism, and the sixth electrostatic mirror prism are in an on state, the fourth, fifth, sixth and seventh ion beams are generated cyclically to provide a selectable number of reflections proportional to a selected time-of-flight. 
     
     
       16. The system of  claim 15 , further comprising:
 a processor coupled to the electrostatic mirror prism arrangement, the processor adapted to control the on and off states of the third and sixth electrostatic mirror prisms to determine the number of reflections in response to the selected time-of-flight. 
 
     
     
       17. The system of  claim 15 , wherein the time-of-flight is user selectable to provide predetermined levels of a mass resolving power and a signal-to-noise ratio. 
     
     
       18. The system of  claim 12 , wherein the first electrostatic mirror prism, the second electrostatic mirror prism, the third electrostatic mirror prism, the fourth electrostatic mirror prism, the fifth electrostatic mirror prism, and the sixth electrostatic mirror prism are coplanar in an energy dispersion plane. 
     
     
       19. A mass analyzing system for time-of-flight (“TOF”) mass spectrometry analysis, the system coupleable to a pulsed ion source providing a first, pulsed ion beam having an input TOF focus, the system comprising:
 an electrostatic mirror prism arrangement comprising:
 a first electrostatic mirror prism having a first plurality of planar electrodes to generate a first retarding electric field to reflect the first ion beam and provide a second, intermediate ion beam having a spatial dispersion of ions proportional to ion kinetic energies, the second ion beam having an second, intermediate TOF focus; 
 a second electrostatic mirror prism spaced apart from the first electrostatic mirror prism by a first predetermined distance and further arranged to have a predetermined first angular offset from the first electrostatic mirror prism, the second electrostatic mirror prism having a second plurality of planar electrodes to generate a second retarding electric field to reflect the second ion beam and converge the spatial dispersion of ions to provide a third, recombined ion beam, the third ion beam having a third TOF focus; 
 a third electrostatic mirror prism having a third plurality of planar electrodes to generate a third retarding electric field to reflect the third ion beam and provide a fourth ion beam having a spatial dispersion of ions proportional to ion kinetic energies, the fourth ion beam having a fourth, intermediate TOF focus; and 
 a fourth electrostatic mirror prism spaced apart from the third electrostatic mirror prism by a second predetermined distance and further arranged to have a predetermined second angular offset from the third electrostatic mirror prism, the fourth electrostatic mirror prism having a fourth plurality of planar electrodes to generate a fourth retarding electric field to reflect the fourth ion beam and converge the spatial dispersion of ions to provide a fifth, recombined ion beam, the fifth ion beam having a fifth, output TOF focus; and 
 
 an ion detector arranged at the fifth, output TOF focus to receive the fifth ion beam, the ion detector adapted to detect a plurality of ions of the fifth ion beam. 
 
     
     
       20. The system of  claim 19 , further comprising:
 a dissociation device adapted to generate a laser beam or an electron beam to fragment molecules of the third ion beam at the third TOF focus. 
 
     
     
       21. The system of  claim 20 , further comprising:
 a processor coupled to the dissociation device, the processor adapted to control the on and off states of the dissociation device to selectively fragment molecules of the third ion beam at the third TOF focus. 
 
     
     
       22. The system of  claim 21 , wherein the processor is further adapted to turn the dissociation device on or off at a selected duty cycle to provide a tandem operating mode for mass spectra having a plurality of fragment molecules and mass spectra having fragment-free molecules. 
     
     
       23. The system of  claim 19 , wherein the electrostatic mirror prism arrangement further comprises:
 a first bandpass filter having a moveable energy bandpass control slit, the first bandpass filter arranged at the second, intermediate TOF focus to selectively allow propagation of ions of the second ion beam having a first selected range of ion kinetic energies; and 
 a second bandpass filter having a moveable energy bandpass control slit, the bandpass filter arranged at the fourth, intermediate TOF focus to selectively allow propagation of ions of the fourth ion beam having a second selected range of ion kinetic energies. 
 
     
     
       24. The system of  claim 19 , wherein the first electrostatic mirror prism, the 30 second electrostatic mirror prism, the third electrostatic mirror prism, and the fourth electrostatic mirror prism are coplanar in an energy dispersion plane. 
     
     
       25. The system of  claim 19 , wherein the third electrostatic mirror prism and the fourth electrostatic mirror prism are not coplanar with the first electrostatic mirror prism and the second electrostatic mirror prism. 
     
     
       26. The system of  claim 19 , wherein the predetermined first and second angular offsets are each greater than or equal to 45° and less than or equal to 135°. 
     
     
       27. A mass analyzing system for time-of-flight (“TOF”) mass spectrometry analysis, the system coupleable to a pulsed ion source providing a first, pulsed ion beam having an input TOF focus, the system comprising:
 a plurality of pairs of electrostatic mirror prisms, each pair of electrostatic mirror prisms of the plurality of pairs of electrostatic mirror prisms comprising:
 a first electrostatic mirror prism having a first plurality of planar electrodes to generate a first retarding electric field to reflect the first ion beam or a next recombined ion beam and provide an intermediate ion beam having a spatial dispersion of ions proportional to ion kinetic energies, the intermediate ion beam having a intermediate TOF focus; and 
 a second electrostatic mirror prism spaced apart from the first electrostatic mirror prism by a first predetermined distance and further arranged to have a predetermined first angular offset from the first electrostatic mirror prism, the second electrostatic mirror prism having a second plurality of planar electrodes to generate a second retarding electric field to reflect the intermediate ion beam and converge the spatial dispersion of ions to provide the next recombined ion beam, the next recombined ion beam having a combined output-input TOF focus; 
 
 a bandpass filter having a moveable energy bandpass control slit, the bandpass filter arranged at at least one intermediate TOF focus of a plurality of intermediate TOF focuses provided by the plurality of pairs of electrostatic mirror prisms, to selectively allow propagation of ions of a corresponding intermediate ion beam having a selected range of ion kinetic energies; and 
 an ion detector arranged at the combined output-input TOF focus to receive the next recombined ion beam provided by a last pair of electrostatic mirror prisms of the plurality of pairs of electrostatic mirror prisms, the ion detector adapted to detect a plurality of ions of the next recombined ion beam. 
 
     
     
       28. The system of  claim 1 , wherein the intermediate TOF focus is located at one-half of the first predetermined distance from the first electrostatic mirror prism.